1. Field of the Invention
This invention relates generally to a mechanism for mounting a printed circuit board, and, more particularly, to a mechanism for latching a printed circuit board into an electrical connector and ejecting the printed circuit board from the electrical connector.
2. Description of the Related Art
In the field of electronics, designers have been continuously reducing the size of components, such as semiconductor chips, to increase the speed and performance of the electronic circuits, and to more efficiently utilize semiconductor real estate. Typically, these semiconductor chips are mounted on a printed circuit board, which is, in turn, coupled to other printed circuit boards through various electrical connectors to form an electrical system, such as a personal computer.
As the semiconductor chips have become smaller, and electrical systems have become more complex, more chips are located on a printed circuit board. As more and more semiconductor chips and electronic circuits are packed onto a printed circuit board, more and more electrical signals are generated and delivered throughout the system, especially to the other printed circuit boards. Commonly, these signals are delivered "off-board" to the other printed circuit boards via an edge connector. That is, a series of metallic tabs are formed along at least one edge of the printed circuit board, and metallic traces interconnect the semiconductor chips with the metallic tabs. The metallic tabs are arranged to coincide with spring loaded metallic tabs or contacts in an edge connector. The edge connector is interconnected with other edge connectors and printed circuit boards so that the electrical signals can be transmitted therebetween.
In systems where the edge connector area cannot be increased in proportion to the number of signals, the individual metallic tabs are necessarily reduced in width to accommodate more metallic tabs. For example, state-of-the-art microprocessor printed circuit boards have over 300 metallic tabs that measure 50 thousandths of an inch wide. The tabs are arranged in a tiered configuration with three tabs every 100 thousandths of an inch. These densely packed contacts can become misaligned with their corresponding edge connector by a relatively minor displacement of only 20 thousandths of an inch. That is, the printed circuit board can become uncoupled or disconnected from its corresponding electrical connector relatively easily. Disconnection, of course, prevents the electrical signals from being properly delivered to other printed circuit boards in the electrical system, which prevents proper operation of the system. Moreover, this relatively minor displacement is difficult to visually detect, and, thus, faulty operation is difficult to diagnose.
The large size and relatively heavy weight of current microprocessor printed circuit boards further exacerbates the alignment problem because of the board's own inertia during minor g-force shocks. That is, even a minor bumping of the electrical system may be enough to cause the printed circuit board to shift and cease proper operation.
Further, the increasing complexity of electrical systems has also resulted in more printed circuit boards being packed into the same or smaller space. Thus, less and less room is available for the electrical system, which necessitates that the boards be closely proximate one another. This close positioning of the printed circuit boards reduces the available envelope for mechanisms useful in fixing the printed circuit boards against longitudinal movement. Accordingly, bulky latching and ejecting mechanisms are not useful in compact, densely packed electrical systems.
Additionally, maintaining and upgrading electrical systems commonly requires that the printed circuit boards be readily accessible, easy to remove, and easy to install. Moreover, it is a significant disadvantage if special tools are required to access, remove, or install the printed circuit boards. Rather, it is highly advantageous if a user of the electrical system can replace a printed circuit board without the use of any special tools.
The present invention is directed to overcoming, or at least reducing the effects of, one or more of the problems set forth above.